For a long time two views competed over why epidemics spread. One held that bad air rising from decaying matter — miasma — causes disease; the other that invisible microorganisms pass from person to person. What is the real cause of illness?
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Germ theory was right. Specific diseases are carried by specific microorganisms, and bad air itself is not the cause.
Pasteur's swan-neck flask experiment showed that decay comes from microbes carried in the air, and Koch isolated and cultured the anthrax and tuberculosis bacilli, establishing a procedure for pinning a disease on its causal organism (Koch's postulates). Handwashing, antisepsis, vaccines, and sanitation all grew from that foundation.
Certain diseases pass directly from person to person via an invisible transmission by contact rather than through the air.
Epidemics are caused by miasma, the foul air rising from decaying matter.
✦ Source needed
The cause of the cholera illness is a specific agent in the water rather than the air.
✦ Source needed
The cause of the disease is transmitted by hands.
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The stench of decaying matter causes disease.
✦ Source needed
Computed from the vote distribution. It is an observation, not a verdict on which claim is right.
Proponents of miasma theory argue that epidemics originate from foul air and stench rising from decaying matter, pointing to the concentration of illness in low, damp, and foul-smelling districts. Conversely, proponents of germ theory argue that specific invisible microorganisms and contact transmit diseases, citing evidence such as water-well cholera clusters, the dramatic drop in puerperal fever through handwashing alone, swan-neck flask experiments, and the isolation of specific bacilli causing anthrax.
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Epidemics are caused by the foul air that rises from decaying matter — miasma. The stench is the cause of the disease.
Cholera and fever strike hardest around stinking marshes and sewers, in the low, damp districts. The statistics show disease concentrating exactly where the bad air is thickest.
Within one and the same stinking district, only the households drawing water from a particular contaminated well fell ill with cholera. The cause is not in the air but a specific agent in the water.
Certain diseases pass directly from person to person by something invisible. There is a causal matter transmitted by contact, not by air.
Mothers examined by doctors coming from the autopsy room died of puerperal fever far more often than those in the ward staffed only by midwives. When I required the doctors to wash their hands in chlorinated lime, the death rate collapsed.
Could the difference between the wards not come down to other conditions — ventilation, say, or crowding?
One perspective holds that targeted antisepsis, such as disinfecting surgical instruments and wounds with carbolic acid, is the primary means to prevent post-operative infection and mortality. Another view emphasizes broad sanitary reforms, such as rebuilding sewers, ensuring clean water supplies, and improving ventilation. While both sides agree that sanitary infrastructure lowers disease rates, they disagree on whether the mechanism is the clearance of foul air or the removal of biological pathogens.
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Disinfect wounds and surgical instruments to destroy the microbes, and post-operative infection and death fall dramatically.
Only one thing changed: handwashing. The ventilation and the ward stayed exactly as they were, and the deaths fell the moment hands were washed. The cause is something carried on the hands.
Boiled broth left in a swan-neck flask stayed fresh despite open contact with the air; snap the neck so dust can settle in, and it spoiled at once. What causes decay is not the air itself but the microbes carried in it.
Every animal dead of anthrax carried the same rod-shaped bacillus. I cultured that organism in pure form, injected it into healthy animals, and the same disease followed. A specific microbe can be shown by procedure to cause a specific disease.
After I began treating the surgical site and the instruments with carbolic acid, the post-operative death rate in my wards dropped markedly.
That may not be the antisepsis at all — the same routine leaves the ward cleaner and better aired, and that could be what helped.
Same ward, same ventilation: only the disinfected operations saw less infection. Antisepsis was the one variable that changed.
Rebuild a city's sewers and water supply and improve ventilation, and epidemics recede. Sanitary reform is the way to stop disease.
Cities that laid large sewers and clean water mains did see cholera and typhoid fall sharply.
I agree the sanitary reforms worked. But they worked because they removed pathogens from the water, not because they cleared away bad air.